1. Field of the Invention
The invention relates to a method and apparatus for effecting a sealed connection of a tubing string to a tubular member positioned down hole in a subterranean well which has had the top end portion thereof severed by either acid, explosion, or the like, hence presenting an irregular, unthreaded or partially threaded upstanding end surface.
2. Description of the Prior Art
It occasionally becomes necessary to effect the severance of a tubing string in a subterranean well at a down hole point in the well by either acid cutting, by an explosive method, or the like. These drastic methods of effecting the severing of the tubing string may be required if the packer or other tool is stuck in the well.
Utilization of acid or explosive cutting of the tubing string at a down hole position necessarily results in the tubing remaining down hole having an irregularly shaped, top end portion. Connectors for such down hole tubing, collaquially called a "pack-off over shot," have heretofore been provided comprising an annular elastomeric sealing element which is mounted within a housing and lowered on the tubing string to a position surrounding the top end of the tubular member. Slips are provided in the housing which are cam actuated to respectively expand and contract into engagement with the inner wall of the housing and the outer wall of the tubular member, and to concurrently impart an axial compressive force on the annular elastomeric material.
In such prior art connectors, the amount of axial force imposed upon the annular elastomeric seal is in no manner limited, and the greater the axial force that is applied through the connector, the greater will be the axial compression force on the seal. This inherently results either in undesirable extrusion of the elastomeric seal material, or an axial collapsing of a portion of the wall of the tubular member tubing engaged by the seal or the blowing out of the wall of the housing containing the seal.
There is, therefore, a need for a sealed connection for an irregular shaped upstanding end of down hole tubular member which will impose sufficient axial compression force on the annular seal to insure that the seal will maintain its integrity under any fluid pressures encountered in the operation of the particular well, yet limits the application of excessive compression forces to the seal by the subsequent manipulative movement of the tubing string.